1. Field of the Invention
This invention relates to a method and apparatus for submerged combustion melting, that is, a method and apparatus in which the hot products of combustion are introduced directly into a material for melting, such as glass, through an opening in the melt containment vessel disposed below the level of the material present in the melt containment vessel.
2. Description of Related Art
The concept of submerged combustion is not new. Most of the burners that have been developed for this purpose are applicable to aqueous systems. However, burners suitable for use in the melting of high melting temperature materials, such as glass, metals, etc. are also known. U.S. Pat. No. 3,260,587 to Dolf et al. teaches a method and apparatus for submerged combustion melting of glass or similar materials in which a burner having an air cooled casing is inserted into a furnace wall, either the furnace side wall or the furnace floor. The burner is provided with means for mixing fuel gas and air, burning them and discharging the combustion products at high temperature and velocity directly into the glass. The hot gases agitate the glass, transferring a high percentage of heat to the glass, thereby rapidly melting the glass. U.S. Pat. No. 3,738,792 to Feng describes a burner for use in submerged combustion applications which is able to use liquid fuels. In both of the '587 patent and the '792 patent, removal of the burner from the furnace for repair or replacement requires that the furnace be shut down to prevent the molten material from flowing out through the burner opening.
This problem is addressed by U.S. Pat. No. 3,563,683 to Hess which teaches a burner for use in submerged combustion applications, which includes a hollow sleeve adapted to receive the burner lining the opening in the furnace wall, which hollow sleeve is provided with passages through which a cooling fluid may flow. Upon removal of the burner from the sleeve, the cooling effect of the cooling fluid flowing through the sleeve is such that the molten material in the furnace adjacent thereto freezes, thereby preventing the molten material from escaping. An alternative solution is described by U.S. Pat. No. 4,203,761 to Rose which teaches a method and apparatus for submerged combustion melting in which the burners extend downward from the furnace roof into the molten bath. In this way, issues associated with burners disposed in the furnace wall below the level of the molten material, such as burner removal and burner clogging, are avoided altogether.
One persistent problem associated with submerged combustion melting using burners disposed in the furnace wall below the level of the molten material is flame stability. In addition, the burners of the prior art physically protrude into the furnace, affecting not only burner service life, but also affecting mixing of the molten material in the furnace.